Many coolant systems, such as, automobile air conditioners, use chemicals called refrigerants to cool air. The refrigerants may be added to the coolant system as liquids, but utilized in the system as gases. These coolant systems operate based on the principle of Gay-Lussac's Law, which is:P/T=P′/T′ where V is constantand where P=pressure, T=temperature, and V=volume. In accordance with this law, as the pressure of a compressed gas increases, its temperature increases. Conversely, as the pressure of the gas decreases, the temperature of the gas decreases. Expansion of a refrigerant gas in a coolant system acts to cool the system containing the refrigerant. Air blown over the cooled system, in turn may be cooled, and provided to a vent where it can cool an interior space, such as an automobile cabin. This is the basic concept of many refrigeration and air conditioning systems.
The ability to achieve cooling by compressing and expanding a gaseous refrigerant may depend to some degree on the level of liquid refrigerant present in the system. In an automobile air conditioning system, several factors may adversely affect the level of refrigerant in the system. For example, the system may be subject to significant swings in temperature and frequent thermal cycling due to the action of the air conditioner itself and the heat produced by the automobile's engine. Under these conditions, joints and fittings may tend to expand and contract, permitting refrigerant to slowly leak out of the system. In another example, the hoses used may be slightly permeable to the refrigerant, which may also permit the refrigerant to slowly leak out of the hoses. Accordingly, maintenance of an automobile air conditioning system may require monitoring the refrigerant level or pressure and periodic re-charging of the refrigerant as indicated.
Typical automotive air conditioners are provided with at least one service port to allow for the addition of refrigerant and checking on the level of refrigerant in the system. The check of refrigerant level and the addition of refrigerant may be attended to by a professional mechanic, however, there is no requirement that a professional carry out these functions. A growing number of automobile owners choose to perform this type of routine maintenance on their vehicles. This market is commonly referred to as the “do-it-yourself” market.
A standard tool used by professionals for servicing automobile air conditioners includes a set of manifold gauges. This device usually includes three hoses and two gauges: one hose connects to a low pressure service port; one hose connects to a high pressure service port; and the third hose connects to the source of refrigerant. The two gauges may be used to measure the pressure at the high and low pressure service ports.
Although manifold gauges are the standard tool used by professional auto mechanics for air conditioner service, several disadvantages may reduce their popularity among do-it-yourself consumers. Manifold gauges can be complicated to use. One must know the approximate ambient temperature and look up the pressure readings of the gauges on a chart to determine if there is sufficient refrigerant in the system. In addition, use of manifold gauges may be dangerous. Because these devices require handling of the high pressure service port of the automobile air conditioner, their use may present a risk of injury to inexperienced consumers. Furthermore, manifold gauges may be relatively expensive for a “do-it yourself” consumer considering the relative infrequency of their use for servicing of a single automobile. Accordingly, there is a need for new methods and apparatus for servicing air conditioners, such as those used in automobiles, which do not have the same drawbacks as manifold gauges.
Various method and apparatus embodiments of the present invention may be used to service air conditioners, such as those used in automobiles. Embodiments of the present invention may allow a consumer to measure the refrigerant pressure in an automobile air conditioner, and to add refrigerant as needed. Additional advantages of embodiments of the invention are set forth, in part, in the description which follows and, in part, will be apparent to one of ordinary skill in the art from the description and/or from the practice of the invention.